Telephonic transmitter



May 6 1924. 1,492,919

M- R- HUTCHISON TELEPHON IC TRANSMITTER Filed April 10. 1919 I 6 Irwmron Hi6 A TTORNE Y Patented May 6, 1924.

UNITED STATES;

PATENT OFFICE.

KILLER REESE HUT CKISON, F LLEWELIlLYN PARK, ORANGE, NEW JERSEY.

TELEPHONIC TRANSMITTER Application filed April 10, 1919. Serial No.288,973.

To all whom it may concern Be it known that I, MILLER Reese Horonrson, acitizen of the United States, and resident of Llewellyn Park, Orange, in

the county of Essex and State of New Jersey, have invented certain newand use ful- Improvements in Telephonic Trans mitters, of which thefollowing is a specification.

My present invention relates to devices for producing electricalvariations corresponding to complex waveforms, particularly thosecharacteristic of human speech and other audible sounds and it includesa new method and a new means for utilizing acoustic vibrations in theair to produce electrical variations in a circuit correspond ingfaithfully thereto.

The invention depends upon the change of resistance of the conductor byreason of the change or variation of the temperature of the conductorand upon possibility of making the conductor sufficiently sensitive tochange its tcmperatureby the acoustic wave movements of particles of airadjacent there to. Every characteristic of an acoustic wave propa atedin the air is accurately represented y alternate to and fro movements ofthe particles at varying rates. These movements vary in distance andrate according to the frequency and intensities of the constituentelements of the wave. In the case of a single frequency, pure sine wave,the velocities and .the rates of change of velocities of each particlefollow the law of the sine and in complex waves the componentfrequencies are represented by alternate accelerations, retardations orreversals supcrposed'on the fundamental swing or movement. Thesevariations of velocity and the variations of air pressure correspondingthereto are recognized by the ear and the brain which translate them inall the various ways and with all the varied significances that soundscan have.

By directing and preferably concentrating these movements of the airupon a sufliciently sensitive conductor their varied movements willroduoe corresponding varied fluctuations in a current passing throughsaid conductor, and by making the conductor of suflicicntly small massas compared with its radiating surface and by making its temperaturevery much higher than that of the surrounding air or other gaseousmedium, the variation in cooling effects due to air or gas movements maybe made to attain a maximum.

Other things being equal, the variations will be proportional to thelength of the conductor. The conductor may bequite long provided it becoiled or otherwise arranged so that its projected length in a directionparallel to the waves is small as compared with the physical length of aquarter wave in the air. This is not difficult since waves of 1000frequency are over a foot long and all of the vowel sounds are belowthat frequency. components as high as 6000 the quarter wave length ismore than half an inch.

Hem-o, while for some purposes I prefer to arrange the heat sensitiveconductor n a plane exactly transverse to the waves, for ordinaryurposes, a short coil having its axis para lel with the waves may beemployed.

The waves in the air may be concentrated and their movements adj acentthe conductor intensified in any desired way. A convenient way selectedfor purposes of illustration herein is to arrange the heat sensitiveelement in an opening communicating with a shallow closed space in therear of an acoustic diaphragm. The waves impinging on Even forfrequencies or frequency the front of the diaphragm cause to and frommovements thereof which will produce a magnified to and fro forcing ofthe air into and out of the restricted opening in which thethermosensitive coil is arranged.

The coil is preferably of some non-oxidizing metal, as for instance,latinum. It is preferably of very small iameter and if desired, may beof the extremely minute diameters attained in Wollaston wire, which ismade by encasing a fine platinum wire corein a massive silver coating,drawing down the composite wire to an extremely small diameter, and thendissolving off the silvel to expose the reduced platinum core.

A more or less diagrammatic illustration of an embodinn nt of myinvention is shown in the accompanying drawings, in which Figure 1 is adiametric section through a vibrates the air is correspondingly expelthrough and drawn into the chamber between, the

transmitter case with the thermo-sensitive coil, the heating battery,the telephone receiver and the circuit connections diagrammaticallyindicated;

. Figure 2 is a similar view of a modification; and

Figure 3 is a similar view showing a relay embodiing the invention. I

In t e rawings, the telephone transmitter casing comprises the front 1,back 2, and

tubular opening 3 in the back. ,The thermo-,.-.

tween the diaphragm and the back of the" casing. The tube or orifice-3in which thecoil or grid of fine wire 4 is located, serves as'abreather. Therefore, as the diaphragn through said breather. The battery6 flowing normally through the coil 4 heats it to a temperature higherthan that of the air,

-preferably very much higher and the alternate movement of the. airproduces a cooling eflect varying by and in accordance with the velocityof said movements, thus causing corresponding variations in theresistance 'of the coil 4. These variations flowing through thetelephone receiver will cause movements of the receiver diaphragm whichwill in turn im art to theair movements corres onding to t e originalsound.

11 certain ases, I may'supply to the space iaphragm and its casing acontinuous, prefera ly gentle flow of air whlch continua {ablepotentiometer indicated in Figure 2.

1y supplies fresh air at normal tem-. peratiire prevents localoverheating of the air adjacent the coil. The conduit 11 dischargingthrough opening 12, Figures 2 and 3, mav be emplolyed for this purpose.

In Figure 3, have shown a relay magnet 13* which may be energized from atele honic circuit to cause vibration of the diap iragm instead ofroducing said vibration by direct action of t e ai'r waves.

Nickel and other metals and alloys as well as platinum may be used forthe thermo-sensitive element and when latinum is used, it may, ifdesired, be heatc to extreme incandescence short of melting.

It will be understood that the battery 6 represents any desired sourceof electrical ener y and that any suitable means may be emp oyed forcontrolling the voltage and amperage of the current. For instance,.thebattery instead of being interposed directly in series with the circuit,may be associated therewith through the medium of an adjust- P asdiagrammatically I claim l. A. telephomc ,transmitting apparatuscomprising an electric circuit, a thermo-sensitive element of extremelysmall cross-section interposed in said circuit, in combination with 'atelephonic, transmitter diaphragm and casing and a restricted passagecommunicating with the transmitter and surrounding said thcrmo-sensitiveelement.

2. A telephonic transmitter comprisin an acoustic diaphragm, a casing.afl'or ing clamping support for the edges of said diaphragm and having asound outlet of small cross-section at the rear of the diaphragm and asound inlet of larger area at the front of the diaphragm, in combinationwith a Wollaston wire rid or coil arranged in said sound outlet an atelephonic transmitting circuit including a battery in series with saidcoil.

Signed at New York cit in the county of New York, and State of ew York,this 8th day of April, A. D. 1919.

MILLER REESE HUTCHISON.

